.container{
	background: #ccc;
	height: 200px;
	width: 400px;
	position: absolute;
	left: 50%;
	top: 50%;
	margin: -100px 0 0 -200px;
}

#left,#right{
	background: #fc0;
	height: 50px;
	width: 50px;
	position: absolute;

}

#left{
	top: 0;
	left: 0;
	border-radius: 0 0 100% 0 ;
}

#right{
	bottom: 0;
	right: 0;
	border-radius:100%  0 0  0 ;

}